Weird growth on scoby

[mona]

I recently started brewing kombucha again, and so far everything is going well. However, today I noticed a weird black growth on the baby scoby in my slightly over fermented jar (it's been 17 days since I've changed the tea). I drained the jar and removed the baby, and picked off the black piece that was growing in the middle. It was slightly hard and kind of twisted, like a wet piece of dried tea leaf, and was embedded and slightly difficult to pick out of the scoby. I am almost certain it's not a tea leaf that remained after brewing as the liquid was clear while fermenting, and when I picked it apart it was not fibrous. Has anyone had a similar experience or know what this might be? I found another piece and took a picture of it: